LM25061PMM-2/NOPB National Semiconductor, LM25061PMM-2/NOPB Datasheet - Page 9

• Manufacturer Part Number: LM25061PMM-2/NOPB
• Description: IC CTLR POS HOTSWAP AUTO 10MSOP
• Manufacturer: National Semiconductor
• Type: Hot-Swap Controllerr

Specifications of LM25061PMM-2/NOPB

• Applications: General Purpose
• Internal Switch(s): No
• Voltage - Supply: 2.9 V ~ 17 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 10-TFSOP, 10-MSOP (0.118", 3.00mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: LM25061PMM-2

Functional Description
The LM25061 is designed to control the in-rush current to the
load upon insertion of a circuit card into a live backplane or
other "hot" power source, thereby limiting the voltage sag on
the backplane’s supply voltage, and the dV/dt of the voltage
applied to the load. Effects on other circuits in the system are
minimized, preventing possible unintended resets. A con-
trolled shutdown when the circuit card is removed can also be
implemented using the LM25061. In addition to a pro-
grammable current limit, the LM25061 monitors and limits the
maximum power dissipation in the series pass device to main-
tain operation within the device Safe Operating Area (SOA).
Power Up Sequence
The VIN operating range of the LM25061 is +2.9V to +17V,
with a transient capability to 20V. Referring to the Block Dia-
gram and
increases, the external N-channel MOSFET (Q1) is held off
by an internal 260 mA pull-down current at the GATE pin. The
strong pull-down current at the GATE pin prevents an inad-
vertent turn-on as the MOSFET’s gate-to-drain (Miller) ca-
pacitance is charged. Additionally, the TIMER pin is initially
held at ground. When the VIN voltage reaches the POR
threshold the insertion time begins. During the insertion time,
the capacitor at the TIMER pin (C
current source, and Q1 is held off by a 2 mA pull-down current
Figure 1
and
Figure
3, as the voltage at VIN initially
T
) is charged by a 5.5 µA
FIGURE 1. Basic Application Circuit
FIGURE 2. LM25061 Application
9
Either current limiting or power limiting for an extended period
of time results in the shutdown of the series pass device. In
this event, the LM25061-1 latches off until the circuit is re-
enabled by external control, while the LM25061-2 automati-
cally restarts with defined timing. The circuit breaker function
quickly switches off the series pass device upon detection of
a severe over-current condition. The Power Good (PGD) out-
put pin indicates when the output voltage is above the pro-
grammed threshold. A programmable under-voltage lock-out
(UVLO) circuit enables the LM25061 when the system input
voltage is above the desired threshold. The typical configu-
ration of a circuit card with LM25061 hot swap protection is
shown in
at the GATE pin regardless of the VIN voltage. The insertion
time delay allows ringing and transients at VIN to settle before
Q1 is enabled. The insertion time ends when the TIMER pin
voltage reaches 1.72V. C
internal 2 mA pull-down current. The GATE pin then switches
on Q1 when V
above the UVLO threshold at the end of the insertion time, Q1
switches on at that time. The GATE pin charge pump sources
20 µA to charge Q1’s gate capacitance. The maximum volt-
age at the GATE pin is limited by an internal 19.5V zener
diode.
As the voltage at the OUT pin increases, the LM25061 mon-
itors the drain current and power dissipation of MOSFET Q1.
In-rush current limiting and/or power limiting circuits actively
Figure
SYS
2.
exceeds the UVLO threshold. If V
T
is then quickly discharged by an
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SYS
is